Thermal acoustic insulation blankets are widely used in various applications including aircraft applications to provide thermal insulation and acoustic damping.
Insulation blankets suitable for use in aircraft insulation systems are typically placed into the cavity between the aircraft fuselage skin panels and the aircraft interior panels. These insulation blankets are typically multilayer assemblies incorporating one or more fire-resistant layers providing a flame spread barrier to the insulation blanket so as to protect passengers of an aircraft in the event of a fire such as a ground fuel fire or a post-crash fire.
The longer it takes for the fire to penetrate the aircraft fuselage, the more time aircraft passengers may have to evacuate the aircraft before being overcome by smoke or heat from the fire.
According to regulations contained in 14 C.F.R. Section, Part 25, 25.856(a), 25.856(b) and part VII of Appendix F, the Federal Aviation Administration (FAA) requires thermal acoustic insulation blankets to provide improved burn-through protection and flame propagation resistance in certain areas of airplanes.
Known thermal acoustic insulation blankets are usually encapsulated within a film covering or bag. FAA burn-through regulations primarily affect the content of the insulation system bags, whereas the FAA flame propagation resistance regulations primarily affect the film coverings to fabricate the bags.
Among drawbacks of the prior art insulation blankets is that, depending on the material of construction, the blankets may contribute to the propagation of fire when exposed to a flame under a radiant heat source.
The film coverings thus typically comprise a barrier outer layer further minimizing moisture uptake and hence weight increase of the insulation blanket due to water entrapment during service.
For instance, US 2013/0092321 (UNIFRAX I LLC; LAMART CORPORATION) 18 Apr. 2013 describes fire barrier laminates wherein the first polymeric flame propagation resistant film may be metallized to minimize moisture absorption, particularly on the outboard side, but optionally also on the inboard side.
There thus remains a need in the art for long lasting, durable thermal and acoustic blankets suitable for use in aircraft fuselage insulation systems providing for a lower permeability to gases and an improved flame spread resistance.